This invention relates to an auto-correlation unit for use in pattern recognition to obtain auto-correlation coefficients as for stored signal samples.
Auto-correlation coefficient C.sub..tau. used in pattern recognition for voice recognition can generally be obtained by the following equation: ##EQU2##
where .tau. indicates the degree of the auto-correlation coefficient sought to be calculated.
Conventional auto-correlation units for voice recognition are comprised of a multiplier and an adder. The multiplication items in the above equation are calculated and .tau. pieces of the auto-correlation coefficients are calculated by adding these results in the adder in order to obtain the cumulative sum thereof.
Those state-of-the-art units for calculation of the auto-correlation coefficients have the disadvantage of requiring expensive multipliers and also complicated circuitry. As a result the auto-correlation unit circuitry within the entire pattern recognition apparatus is proportionately large and auto-correlation calculation demands a greater amount of time during recognition.